Cotton canopy reflectance under variable solar zenith angles: Implications of use in evapotranspiration models     

Christopher M. U. Neale  Maria P. Gonzalez-Dugo  Angelica Serrano-Perez  Isidro Campos  Luciano Mateos 《水文研究》2021,35(6):e14162

Evapotranspiration (ET) is an important parameter in hydrologic processes and modelling. In agricultural watersheds with competing uses of fresh water including irrigated agriculture, estimating crop evapotranspiration (ET_c) accurately is critical for improving irrigation system and basin water management. The use of remote sensing-based basal crop coefficients is becoming a common method for estimating crop evapotranspiration for multiple crops over large areas. The Normalized Difference Vegetation Index (NDVI) and the Soil Adjusted Vegetation Index (SAVI), based on reflectance in the red and near-infrared bands, are commonly used for this purpose. In this paper, we examine the effects of row crop orientation and soil background darkening due to shading and soil surface wetness on these two vegetation indices through modelling, coupled with a field experiment where canopy reflectance of a cotton crop at different solar zenith angles, was measured with a portable radiometer. The results show that the NDVI is significantly more affected than the SAVI by background shading and soil surface wetness, especially in north–south oriented rows at higher latitudes and could lead to a potential overestimation of crop evapotranspiration and irrigation water demand if used for basal crop coefficient estimation. Relationships between the analysed vegetation indices and canopy biophysical parameters such as crop height, fraction of cover and leaf area index also were developed for both indices.  相似文献   

Area usage estimation and spatiotemporal variability in distribution patterns of southern right whales,Eubalaena australis,of southern Brazil          下载免费PDF全文

Eduardo Pires Renault‐Braga  Karina Rejane Groch  Paulo A. de Carvalho Flores  Eduardo R. Secchi  Luciano Dalla‐Rosa 《Marine Ecology》2018,39(3)

Southern right whales—Eubalaena australis (Desmoulins, 1822)—migrate seasonally from high‐latitude feeding grounds to coastal breeding and calving grounds at lower latitudes such as the southern coast of Brazil. Understanding how these whales are distributed along the coast is important for monitoring their postwhaling recovery and defining management strategies. In this study, we applied Kernel density estimators to aerial survey data to determine main occurrence and concentration areas of right whales in southern Brazil and investigate inter‐ and intra‐annual distribution patterns between 2003 and 2012. Our results show considerable variation in area usage within and among years, and changes in the general distribution pattern of right whales in the last years of the study. Intra‐annually, higher concentration area tended to expand from July to September and decrease in November. Some areas stood out as high‐density areas for right whales: Ribanceira/Ibiraquera, Itapirubá Sul/Sol, and from Arroio to Gaivota. Some evidences also suggest preferential areas for mother–calf pairs. The higher concentration area of right whales in southern Brazil was estimated at 52,541 km² and the occurrence area was 682.69 km², which is the whole study area. As right whale distribution in the region is likely expanding due to this population's current recovery, our study provides essential information for management plan of the Right Whale Environmental Protection Area.  相似文献   

Five years of thermal intra-urban monitoring in Florence (Italy) and application of climatological indices     

Martina Petralli  Luciano Massetti  Simone Orlandini 《Theoretical and Applied Climatology》2011,104(3-4):349-356

This paper presents 5?years of detailed intra-urban thermal measurements carried out in Florence (Italy) by a network of 25 air temperature stations. Daily, hourly, and degree-day indices were applied to hourly data to evaluate the difference within the complex urban environment of Florence. Stations were grouped in four clusters with similar thermal regimes in each season. Our results evidence a mean difference of almost 2°C between the hottest and the coolest cluster in all seasons. Furthermore, the coolest cluster had on average more than ten frost days in winter and the hottest cluster more than 12 summer days in summer. The intra-urban difference of tropical nights was even more evident, with values of 42 versus 10?days between the hottest and the coolest cluster during the summer period. The results of this study contribute to quantify the thermal intra-urban differences in the city of Florence, suggesting important applications in plant phenology, aerobiology, human health, urban planning, and biometeorology.  相似文献   

Process-based design flood estimation in ungauged basins by conditioning model parameters on regional hydrological signatures     

Daniela Biondi  Davide Luciano De Luca 《Natural Hazards》2015,79(2):1015-1038

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On Flare-CME Characteristics from Sun to Earth Combining Remote-Sensing Image Data with <Emphasis Type="Italic">In Situ</Emphasis> Measurements Supported by Modeling     

Manuela Temmer  Julia K. Thalmann  Karin Dissauer  Astrid M. Veronig  Johannes Tschernitz  Jürgen Hinterreiter  Luciano Rodriguez 《Solar physics》2017,292(7):93

We analyze the well-observed flare and coronal mass ejection (CME) from 1 October 2011 (SOL2011-10-01T09:18) covering the complete chain of effects – from Sun to Earth – to better understand the dynamic evolution of the CME and its embedded magnetic field. We study in detail the solar surface and atmosphere associated with the flare and CME using the Solar Dynamics Observatory (SDO) and ground-based instruments. We also track the CME signature off-limb with combined extreme ultraviolet (EUV) and white-light data from the Solar Terrestrial Relations Observatory (STEREO). By applying the graduated cylindrical shell (GCS) reconstruction method and total mass to stereoscopic STEREO-SOHO (Solar and Heliospheric Observatory) coronagraph data, we track the temporal and spatial evolution of the CME in the interplanetary space and derive its geometry and 3D mass. We combine the GCS and Lundquist model results to derive the axial flux and helicity of the magnetic cloud (MC) from in situ measurements from Wind. This is compared to nonlinear force-free (NLFF) model results, as well as to the reconnected magnetic flux derived from the flare ribbons (flare reconnection flux) and the magnetic flux encompassed by the associated dimming (dimming flux). We find that magnetic reconnection processes were already ongoing before the start of the impulsive flare phase, adding magnetic flux to the flux rope before its final eruption. The dimming flux increases by more than 25% after the end of the flare, indicating that magnetic flux is still added to the flux rope after eruption. Hence, the derived flare reconnection flux is most probably a lower limit for estimating the magnetic flux within the flux rope. We find that the magnetic helicity and axial magnetic flux are lower in the interplanetary space by ～?50% and 75%, respectively, possibly indicating an erosion process. A CME mass increase of 10% is observed over a range of \({\sim}\,4\,\mbox{--}\,20~\mathrm{R}_{\odot }\). The temporal evolution of the CME-associated core-dimming regions supports the scenario that fast outflows might supply additional mass to the rear part of the CME.  相似文献   

A wave model for the Great Barrier Reef   总被引：1，自引：0，他引：1  

Thomas A. Hardy  Luciano B. Mason  Jason D. McConochie 《Ocean Engineering》2001,28(1):1869

A new wind wave generation model, WAMGBR, is presented that has been adapted from WAM especially for use in the complex geometry of the Great Barrier Reef. A technique (reef parameterization) has been presented that incorporates sub-grid scale dissipation caused by coral reefs. Three other improvements to WAM have been proposed. An explicit/implicit finite difference scheme has been implemented that allows for more efficient modelling (longer time steps) while maintaining diffusive characteristics that are at least as good as those of WAM. An offset in discrete angles creates more uniform diffusive characteristics. And, a transformed spherical coordinate system allows for more efficient grid sizes and smaller grid dependent refraction. Comparisons between modelling techniques and between model and measured data show that WAMGBR produces very good results in the difficult challenge of modelling both non-cyclonic and tropical cyclone waves in the geographically complex environment of the Great Barrier Reef.  相似文献   

Remote estimation of surficial seafloor properties through the application Angular Range Analysis to multibeam sonar data   总被引：2，自引：2，他引：2  

Luciano Fonseca  Larry Mayer 《Marine Geophysical Researches》2007,28(2):119-126

The variation of the backscatter strength with the angle of incidence is an intrinsic property of the seafloor, which can be used in methods for acoustic seafloor characterization. Although multibeam sonars acquire backscatter over a wide range of incidence angles, the angular information is normally neglected during standard backscatter processing and mosaicking. An approach called Angular Range Analysis has been developed to preserve the backscatter angular information, and use it for remote estimation of seafloor properties. Angular Range Analysis starts with the beam-by-beam time-series of acoustic backscatter provided by the multibeam sonar and then corrects the backscatter for seafloor slope, beam pattern, time varying and angle varying gains, and area of insonification. Subsequently a series of parameters are calculated from the stacking of consecutive time series over a spatial scale that approximates half of the swath width. Based on these calculated parameters and the inversion of an acoustic backscatter model, we estimate the acoustic impedance and the roughness of the insonified area on the seafloor. In the process of this inversion, the behavior of the model parameters is constrained by established inter-property relationships. The approach has been tested using a 300 kHz Simrad EM3000 multibeam sonar in Little Bay, NH. Impedance estimates are compared to in situ measurements of sound speed. The comparison shows a very good correlation, indicating the potential of this approach for robust seafloor characterization.  相似文献   

Refractory Black Carbon Results and a Method Comparison between Solid-state Cutting and Continuous Melting Sampling of a West Antarctic Snow and Firn Core     

Luciano MARQUETTO  Susan KASPARI  Jefferson Cardia SIMOES  Emil BABIK 《大气科学进展》2020,37(5):545-554

This work presents the refractory black carbon(rBC)results of a snow and firn core drilled in West Antarctica(79°55'34.6"S,94°21'13.3"W)during the 2014?15 austral summer,collected by Brazilian researchers as part of the First Brazilian West Antarctic Ice Sheet Traverse.The core was drilled to a depth of 20 m,and we present the results of the first 8 m by comparing two subsampling methods—solid-state cutting and continuous melting—both with discrete sampling.The core was analyzed at the Department of Geological Sciences,Central Washington University(CWU),WA,USA,using a single particle soot photometer(SP2)coupled to a CETAC Marin-5 nebulizer.The continuous melting system was recently assembled at CWU and these are its first results.We also present experimental results regarding SP2 reproducibility,indicating that sample concentration has a greater influence than the analysis time on the reproducibility for low rBC concentrations,like those found in the Antarctic core.Dating was carried out using mainly the rBC variation and sulfur,sodium and strontium as secondary parameters,giving the core 17 years(1998?2014).The data show a well-defined seasonality of rBC concentrations for these first meters,with geometric mean summer/fall concentrations of 0.016μg L^?1 and geometric mean winter/spring concentrations of 0.063μg L^?1.The annual rBC concentration geometric mean was 0.029μg L^?1(the lowest of all rBC cores in Antarctica referenced in this work),while the annual rBC flux was 6.1μg m^?2 yr^?1(the lowest flux in West Antarctica records so far).  相似文献   

Photoelectric activity of the shell staro And: New observations and discussion     

Michele Bossi  Gianantonio Guerrero  Luciano Mantegazza  Marco Scardia 《Astrophysics and Space Science》1980,72(2):433-437

Photoelectric observations of the shell staro And, obtained in 1979, are presented. The star shows variations of some hundredth of magnitudes during a few hours. The trend to retake the values of the luminosity and colour indices prior to the reduction happened between JD 42,714-27, seems to continue. We also give a qualitative model which explains satisfactorily the main features observed after the 1975 shell episode.  相似文献   

Study of the variability of the Delta Scuti stars     

Michele Bossi  Gianantonio Guerrero  Luciano Mantegazza  Marco Scardia 《Astrophysics and Space Science》1981,79(2):463-468

Photoelectric observations of the suspected Delta-Scuti star HR 5492 are given. The present data do not show any light variation greater than 0.01 mag. In spite of the very small light variations, the data analysis shows the presence of two periodicities, which are statistically significant. While the longest period (1. _. ^d 296) cannot be justified with the present data, the shorter one (0. _. ^d 044) is in excellent agreement with the hypothesis of an F4V star that is radially pulsating in the fundamental mode, even if this star is well outside the cold border of the instability strip.  相似文献